This invention generally relates to a surgical instrument for cutting and removing biological tissue. In particular, the present invention is effective for intraocular surgeries, such as vitrectomy, requiring removal of vitreous or pathologic membranes from the interior of an eye. The vitreous humor fills a large portion of the eye interior behind the lens. It is relatively tough tissue composed of rather complex substance including long protein molecules joined by patches of secondary protein molecules. Typically, a vitrectomy involves removing vitreous in bulk and simultaneously filling the void area with saline. Such a surgery further involves precision removal of vitreous base aligned to the retinal surface.
The intricate procedures of a vitrectomy demand high precision tools that are sufficiently small to enable surgical maneuvering within the interior of a human eye. Among the instruments used in intraocular surgeries, those employing a small outer tube with an opening near one end and an inner member providing a cutting means have been in use for some time. These instruments have shown varying effectiveness for cutting and removing vitreous depending on the degree of required surgical precision. In particular, such instruments have operated reasonably well for removing bulk vitreous in the core of vitreous humor where the precision requirement is less critical. However these instruments suffer from lack of heightened precision and performance, for example, for removing denser vitreous base which is more firmly adherent to the retinal surface. As a result, such an instrument tends to cut away the healthy retinal tissue along with vitreous, possibly causing hemorrhage and damage to the retina.
Consequently, a need exists for a high precision instrument suitable for an intraocular surgery, such as vitrectomy, which provides greater precision and safety for removing vitreous without compromising performance. It is further desired that such an instrument provide a means for treating and removing vitreous base near the retinal surface without damaging the healthy tissues of the retina.